Biomimetic engineering of active Zn-doped macrocyclic polyamine carbon dots as organophosphorus hydrolases-like nanozymes for colorimetric and fluorescence on-site detection of methyl-paraoxon.

Organic phosphate esters compounds, especially methyl-paraoxon (MP), pose a serious threat to the environment and human health. The development of robust organophosphorus hydrolases (OPHs)-like nanozymes to mimic natural enzymes is paramount for on-site monitoring MP. Herein, we reported a biomimetic engineering of highly active OPHs-like nanozymes through Zn-doped macrocyclic polyamine carbon dots (DOTA(Zn)-CDs). XPS confirmed ZnN coordination, while FTIR revealed macrocyclic polyamine frameworks with Zn-O/N coordination shifts, together mimicking the histidine‑zinc centers of native OPHs. This design induced a remarkable improvement in OPHs-like activity, demonstrated by a superior catalytic efficiency and a significant enhancement in adsorption affinity for MP hydrolysis, as confirmed by kinetic assays and density functional theory calculations. DOTA(Zn)-CDs nanozymes served as a dual-mode sensing platform, enabling the enhancement of detection performance. This system achieved a low detection limit of 1.55 μM and 2.57 μM for colorimetric and fluorescence detection of MP, alongside exceptional selectivity against interfering species and promising stability for 35 days. Finally, a portable DOTA(Zn)-CDs-based gelatin cube sensor was successfully constructed for practical, on-site detection. This work provides a fundamental strategy for designing efficient OPHs-like nanozymes by biomimetic active site engineering and underscores their significant potential for rapid environmental, agricultural and food detection.